It is obvious, that Paul did NOT consider the obedience to the Mosaic Law, in all its details (first and foremost the circumcision, key symbol and distinction of the Jews vs the Gentiles), essential for salvation. This is crystal clear from plenty of passages from his letters. I believe these two will do:

For circumcision has its value if you practice the law, but if you break the law, your circumcision has become uncircumcision. (Rom 2:25)

Now, what "God’s commandments" is Paul referring to, and of what "law"? ObviouslyNOT the detailed 613 commandments (613 mitzvot) contained in the Torah, because the circumcision is, once again, one of them, nay the key symbol of the Mosaic Law (see Gen 17:10-14; Lev 12:3; see also Wikipedia > Brit milah).

Owe no one anything, except to loveone another, for the one who loveshis neighbor has fulfilled the law. (Rom 13:8)

For in Christ Jesus neither circumcision nor uncircumcision carries any weight – the only thing that matters is faith working through love. (Gal 5:6)

Does this mean that Paul was against the respect of the Mosaic Law for the Jews, who had been brought up in its detailed obedience? Not at all! See the first verse that I quoted in its context:

18 Was anyone called after he had been circumcised? He should not try to undo his circumcision. Was anyone called who is uncircumcised? He should not get circumcised. 19 Circumcision is nothing and uncircumcision is nothing. Instead, keeping God’s commandments is what counts. 20Let each one remain in that situation in life in which he was called. (1Cor 7:18-20)